1. Field of the Invention
The present invention relates to the liquid chamber of an ink jet recording head, and a method for manufacturing an ink jet recording head capable of maintaining bubbles stably in the ink supply system, as well as performing stable ink discharges continuously. More particularly, the invention relates to an ink jet recording head provided with a structure specifically arranged to enable bubbles to be kept stably in the ink supply system thereof, and also, relates to the method of manufacture therefor.
2. Related Background Art
In recent years, along with the popularization of computers, various kinds of application equipment have been developed vigorously. Particularly, remarkable is the development and of various kinds office automation of equipment such as copying machines, facsimile equipment, word processors, and personal computers.
An output devices as a printer, has become prerequisite as the output of the data, documents, and the like processed by such office automation equipment.
Conventionally, printer of various kinds, there have been used, such as a wire-dot printer or other impact type printer, a laser beam printer which uses an electrostatic copying system, and a thermal transfer printer or other non-impact type printer. In recent years, attention has been given to the excellent characteristics of the performance of the ink jet recording printer, and the developments of various kinds of ink jet type printers are in progress.
It is of course desirable to produce beautiful and precise prints and images by use of a printer, and the objectives of the ink jet printer technologies and techniques including improving such image formation.
To this end, the ink jet recording head should be able to discharge ink at higher speeds in higher density, first of all, by use of smaller ink discharge nozzles.
Then, for the ink jet recording head, such smaller ink discharge nozzles should be arranged closely to enhance its performance. To achieve these objectives, there is known the method of manufacture which uses the microlithography technologies to execute fine processing for the provision of many of discharge ports which are arranged closely.
FIG. 4 is a view (perspective view of the outer appearance) which shows a structural example of an ink jet head manufactured as described above. In FIG. 5, heaters 101 are formed on a silicon substrate 100 (not shown), for example. Then, a wall is formed on the heaters by use of photosensitive resin for the formation of nozzles and liquid chamber, and, further, a glass plate (ceiling plate) 107, which is provided with the liquid chamber 114 and the supply opening, is bonded to the wall thus formed (see FIG. 2H). Then, lastly, the ink tube is bonded to it, thus completing an ink jet head. Here, the nozzles are arranged at pitches of 360 dpi, for example.
When ink is discharged from an one nozzle in an ink jet recording head provided with a plurality of nozzles, the ink that resides behind this nozzle moves backward in the direction of the liquid chamber in reaction to the kinetic energy exerted by the discharged ink droplet, thus causing the resultant pressure changes in the liquid chamber. The pressure changes thus exerted cause the vibrations of the menisci of nozzles, which are not engaged in discharging at that time.
When such vibration of menisci takes place, an ink droplet may become larger than when the menisci are stationary if, for example, ink is discharged from a certain nozzle whose meniscus is pushed out forward or an ink droplet may become smaller if it is discharged from a certain nozzle whose meniscus is pulled back at that time.
As described above, the pressure changes in the liquid chamber caused by ink discharges produce unfavorable effect on the nozzles of a head as a whole, which may impede the continuous performance of stable discharges and decrease print quality inferior.
Particularly when the number of nozzles is large or the driving frequency is higher, the unfavorable effect of the meniscus vibration becomes greater and may even make it impossible to obtain continuous discharges.
In order to prevent the menisci from being vibrated, a dumper is provided for the liquid chamber or ink supply system in some cases for the suppression of the pressure changes in the liquid chamber.
As a first prevention measure, the ink supply tube is formed by an elastic material such as silicon tube so as to absorb the pressure vibrations. However, this method is not good enough to obtain the anticipated effect unless the supply tube is located in the vicinity of the nozzles. As a result, the designing freedom is extremely limited. Also, if the numbers of nozzles is increased, the supply tube will be positioned away from them inevitably. Then, this first preventive measure is no longer effective. Also, since the silicon tube has a good gas permeability, air tends to penetrate this tube and create bubbles in it, hence impeding the ink supply after all.
As a second preventive measure, bubbles are induced into the interior of the liquid chamber so as to absorb the pressure vibrations. However, this method is not good enough, either, because with a bubble trapping structure formed in the liquid chamber, bubbles are dissolved into ink and disappear as time elapses even if bubbles are provided in such trap when ink is initially filled in it.
Also, if the head itself is structured so as to take in bubbles easily, it becomes difficult, on the other hand, to maintain bubbles in a stabilized condition. As a result, the ink supply becomes difficult to maintain causing disabled discharge unless bubbles are removed from the nozzles or ink supply system by means of frequent recovery operations or the like.
As described above, there has been no way in the conventional art to suppress the ink pressure vibrations in the liquid chamber without affecting the operations of other parts, not to mention the permanent control thereof.